1. Field of the Invention
The present invention relates to an overhead cam shaft type engine for being installed on a vehicle such as a motorcycle, with a starter motor being attached to a surface of a crank case thereof.
2. Description of Related Art
An overhead cam shaft V-type engine mounted on a motorcycle and having a cam shaft provided in a cylinder head has been known, wherein a starter motor and an oil filter are attached respectively to a front face of a crank case and a front face of an oil pan (see Japanese Published Unexamined Patent Application No. Hei 10-141039).
The above conventional overhead cam type engine is mounted horizontally on a vehicle so that a crank shaft extends in the transverse direction. In the mounted state of the engine, a front cylinder of a front bank is inclined forward and a rear cylinder of a rear bank is inclined backward. A cylinder head is mounted to each of the front and rear cylinders, and an intake cam shaft and an exhaust cam shaft for actuating an intake valve and an exhaust valve through a valve operating mechanism are mounted in the cylinder head. Cam sprockets are mounted respectively on left end portions of the intake and exhaust cam shafts in the front cylinder. Furthermore, a cam shaft driving chain is stretched between the cam sprockets and a driving sprocket mounted on a left end portion of the crank shaft while being entrained on those sprockets, whereby the rotation of the crank shaft is transmitted to both of the cam shafts. Cam sprockets are also mounted on right end portions of the intake and exhaust cam shafts in the rear cylinder. Furthermore, a cam shaft driving chain is stretched between the cam sprockets and a driving sprocket mounted on a right end portion of the crank shaft while being entrained on those sprockets, whereby the rotation of the crank shaft is transmitted to both of the cam shafts.
On the left end portion of the crank shaft are mounted an AC generator and a starter driven gear which is positioned adjacent the AC generator. A starter motor is attached to the front face of the crank case. Upon start-up of the engine, the rotation of the starter motor is transmitted to the crank shaft via a gear train which comprises a pinion gear and a reduction gear and through the starter driven gear mounted on the crank shaft.
In the conventional art referred to above, since the driving sprocket, cam shaft driving chain and cam sprockets, which constitute the cam shaft driving mechanism in the front cylinder, the cam shaft driving mechanism and the gear train are provided on the left end portion of the crank shaft. In this case, since it is necessary to avoid interference of both the cam shaft driving mechanism and the gear train, it has so far been difficult to mount the starter motor at an upper position of the front face of the crank case. Therefore, in the conventional art being considered, it is inevitably required that an oil filter, which is also mounted in front of the engine like the starter motor, be attached to the front face of the oil pan mounted to a lower portion of the crank case. This restricts, for example, the arrangement of an exhaust pipe extending from the front cylinder.